Rapid antigen testing for Covid-19 is not as accurate as RT-PCR testing for Covid-19, the Centers for Disease Control and Prevention said Thursday – often even more inaccurate than advertised.
The rapid tests may miss many cases of disease, the CDC-led team said. And they also often tell people that they are infected when in fact they are not.
Antigen tests are usually cheaper than polymerase chain reaction or PCR tests, and can return results in as little as 15 minutes. Multiple tests in both regions have received emergency use approval from the Food and Drug Administration, but a study published in the CDC Weekly Morbidity and Mortality Report found that antigen testing was not only as accurate as PCR testing, but not they were as accurate as reported when the FDA granted emergency approval.
“Among people who were reporting COVID-19 symptoms at the time the samples were collected, the Sofia antigen test was less accurate than that reported in the FDA’s Emergency Use Authorization,” the CDC-led team wrote. Antigen testing in this study had an 80% sensitivity rate, compared to 97% previously reported.
“For people who were asymptomatic at the time samples were collected, the accuracy was significantly lower – only 41% of RT-PCR samples were also positive with antigen testing and, in this population, the Most advanced antigen tests are ‘false positive’, which is when someone tests positive but does not have the virus. “
The researchers analyzed the trials at two Wisconsin universities by administering a Sofia Quidel antigen test and a PCR test to both sympathetic and asymptomatic participants. Antigen tests quickly look for evidence about the virus, which PCR tests take longer but work by enhancing genetic material from the virus.
“The Sofia rapid antigen test was not as accurate as RT-PCR for the detection of SARS-CoV-2 infections in students and faculty tested at two universities in Wisconsin,” the researchers wrote. “Antigen test accuracy was lowest among study participants who showed no (asymptomatic) symptoms,” he said.
Researchers said antigen tests may still be valuable in disease control because they are cheaper and faster, and may be more affordable than PCR tests. But results from antigen tests should be packaged with a more accurate test.
“To account for reduced test accuracy of antigen tests, CDC recommends considering an FDA-authorized molecular test test, such as RT-PCR, following negative antigen test results in people with COVID-19 symptoms, and following positive antigen test results. in asymptomatic people, ”said researchers.